The present invention relates to a transparent high impact vinyl aromatic polymer and a process for preparing high impact vinyl aromatic polymer by continuous anion polymerization method.
Even though the general purpose polystyrene (GPPS) resin has many merits, such as, cheap price, high processibility, transparency and rigidity, the ductility and durability of resin are not sufficient. To overcome such defects, high impact polystyrene (HIPS) has been developed. Such HIPS has improved the brittleness of polystyrene resin, by dispersing the polybutadiene particles in the polystyrene. However, such high impact polystyrene has a defect of opacity, and it has been required to develop transparent high impact polystyrene.
Commercially manufactured transparent high impact polystyrene resin has been produced according to free radical polymerization of styrene in the presence of the dissolved rubber. According to the types of rubber, various kinds of transparent high impact polystyrene have been manufactured. Japanese laying-open patent No. 2000-61444 and No. 1985-181112 disclosed the high gloss and high impact polystyrene prepared after dissolving butadiene rubber to the styrene monomers. Further, lots of styrene-butadiene block copolymers have been disclosed in JP 88-48317, UK 1,490,625, JP 1993-88006, JP 1992-132112, U.S. Pat. No. 5,349,013 and U.S. Pat. No. 4,839,418, Even though various types of transparent high impact polystyrene have been manufactured using various types of rubber, all of them have been manufactured according to radical polymerization method.
On the other hand, there have been many researches regarding the development of transparent high impact polystyrene having high ductility and durability. As a part of research, polystyrene block copolymer has been suggested by anion polymerization method in the presence of organic metal compound initiator.
U.S. Pat. Nos. 4,584,346; 5,705,569 and 6,096,828 disclosed various block copolymers which are prepared by charging initiators and monomers in many times using anion polymerization methods. Even though obtained polymer have high impact and high mechanical polystyrene properties, they are hard to be manufactured because of their complicate batch process and low productivity.
On the other hand, Japanese laying-open patent No. 1981-28925 disclosed simple block copolymer represented by S-B/S, wherein S represents a vinyl aromatic block and B/S represents a tapered block by simultaneous or sequentially charging conjugated diene monomers and aromatic monomers. However, such method also showed the decline of productivity and physical property since this method is also a batch process.
Contrarily, U.S. Pat. No. 5,795,938 disclosed the high impact polystyrene which is manufactured by continuous anion polymerization method using different 2 tube reactors. In this disclosure, the polymerization method comprising i) polymerizing the polystyrene in one reactor; ii) polymerizing the styrene-butadiene block copolymer in the other reactor; and mixing the obtained polymers to introduce impact-resistance part was disclosed. However, such method might be regarded as only a simple mixing method of each different 2 polymers.
As described above, the known anion polymerization methods to prepare block copolymer using organic metal compound as an initiator have many defects, for example, the complexity of reaction steps to obtain multi-block and multi-component copolymer for obtaining the balance of various properties, the limitation of productivity caused by batch process, and the limitation of properties of obtained copolymer.
Therefore, there is a need for developing transparent high impact polymers, especially transparent high impact polystyrene resin, using continuous agitation reactor rather than conventional tube reactor. The present invention relates to a continuous anion polymerization method having better productivity rather than batch process to manufacture transparent high impact polymer in the forms of radial having more than 3 linear or branched chain or mixture of them.
To complete the present invention for manufacturing transparent high impact polymers, we have developed the continuous process by charging and the polymerizing the initiator, vinyl aromatic monomers and conjugated dienes continuously in the continuous agitation reactor. Further, the polymerization method of the present invention affords the many merits, such as, the control of polymerization heat, appropriate distribution of molecular weight offering the excellent physical properties of final product and high productivity. After polymerization, final transparent high impact polymers are prepared in the forms of linear, radial or mixture of them using multi-functional compounds or terminator.
Further, the advantageous effects of present invention can be exemplified as follows; i) control of molecular weight, distribution, branch density which can not be accomplished by free radical polymerization; ii) minimizing the accelerated reaction or gel formation which occurs in step reaction; iii) minimizing the amount of polymerization solvent; and iv) preparation of multi-component polymer mixed with linear and non-linear structure using multi-functional compounds.
In the other words, the present invention affords the multi-structural polymer contained with linear and non-linear structure, for example, chain, branch, radial or mixture of them by anion polymerization method at the agitation continuous reactor using vinyl aromatic monomers, conjugated diene monomers and multi-functional compounds. Further, the control of multi-functional compounds enables the control of reaction which has not been accomplished by conventional anion polymerization method. Of course, the present invention affords the polymer having excellent physical properties.
The object of present invention is to provide a continuous anion polymerization method for preparing transparent high impact vinyl aromatic polymer comprising the steps of: i ) charging and polymerizing vinyl aromatic monomers and initiator to obtain vinyl aromatic polymer in the presence of solvent and polar organic compounds in the first reactor (1a); ii) continuously charging and polymerizing vinyl aromatic monomers and conjugated diene monomers to the vinyl aromatic polymer obtained in the first reactor to obtain tapered vinyl aromatic polymer chain in the presence of organic solvent in the second reactor (1b); iii) continuously charging and polymerizing vinyl aromatic monomers and multi-functional compounds to the vinyl aromatic polymer chain obtained in the second reactor to obtain high impact vinyl aromatic polymer in the presence of organic solvent in the third reactor (1c); and iv) terminating the reaction with terminator and removing the remaining hydrocarbon solvent and unreacted monomers to obtain transparent high impact vinyl aromatic polymer having number average molecular weight: 20,000xcx9c1,000,000 and molecular weight distribution: 1.1xcx9c20, wherein the molar ratio of charged compounds is 100 mole of vinyl aromatic monomer/1xcx9c100 mole of conjugated diene monomer/0.01xcx9c1 mole of initiator; the amount of organic solvent is 50xcx9c500 (w/v) % of total reactant; and the polymerization temperature is 30xcx9c16 0xc2x0 C.
Said vinyl aromatic monomer is at least one selected from the group consisting of styrene, xcex1-methyl styrene, bromo-styrene and mixture of them. Further, said conjugated diene monomer is at least one selected from the group consisting of 1,3-butadiene, 2-methyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and mixture of them.
Said hydrocarbon solvent is at least one selected from the group consisting of cyclohexane, benzene, n-hexane, n-heptane, toluene, ethyl benzene, xylene, tetrahydrofuran, diethylether and mixture of them. Further, said polymerization initiator is at least one selected from the group consisting of n-butyl lithium, sec-butyl lithium, tert-butyl lithium, methyl lithium, ethyl lithium, phenyl lithium and mixture of them.
Said multi-functional compounds is at least one selected from the group consisting of halogen, functional vinyl aromatic, isocyanate, ester, anhydride, lactone, aldehyde, epoxide, ketone and mixture of them. In particular, divinylbenzene, 1,2,4-trivinylbenzene, 1,3-divinylnaphtalene, 1,3,5-trivinyl-naphtalene, 2,4-divinylbiphenyl-p-diisopropenenylbenzene and mixture of them can be used as vinyl aromatic compound. Other multi-functional compounds can be exemplified as epoxified carbohydrate, organo alkyl phosphite, arylalkyl phosphite, multi-functional isocyanate, multi-functional imine, multi-functional aldehyde, multi-functional halide, multi-functional metal halide. Further, methanol, ethanol, isopropanol, water or carbon dioxide can be used as a terminator.